Liquid ejecting head and liquid ejecting apparatus

ABSTRACT

A liquid ejecting head which includes a flow passage forming substrate that has pressure generating chambers which communicate with nozzles capable of ejecting a liquid, pressure generating elements which apply pressure to the pressure generating chambers in order to eject the liquid from the nozzles, lead electrodes that supply electric signals to the pressure generating elements, wiring substrates that supply the electric signals to the lead electrodes, and a supporting member that supports the wiring substrates so as to raise the wiring substrates from a surface of the liquid ejecting head having the lead electrodes provided thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of prior U.S. patentapplication Ser. No. 12/367,364 filed Feb. 6, 2009, which patentapplication is incorporated herein by reference in its entirety.Furthermore, the entire disclosures of Japanese Patent Application Nos.2008-029800, filed Feb. 8, 2008 and 2008-251844, filed Sep. 29, 2008 areexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a liquid ejecting head and a liquidejecting apparatus. More particularly, the present invention relates toan ink jet recording head capable of discharging a liquid ink from aplurality of nozzles.

2. Related Art

One example of a liquid ejecting head currently known in the art is anink jet recording head that discharges ink as a plurality of inkdroplets. Typically, an ink jet recording head includes a flow passageforming substrate that has pressure generating chambers whichcommunicate with nozzles and a communicating portion which communicateswith the pressure generating chambers, piezo-electric elements that areformed on one surface of the flow passage forming substrate, and aprotective substrate that is bonded to one surface of the flow passageforming substrate which includes piezo-electric element holding portionsfor holding the piezo-electric elements. In addition, an IC, which is adriving circuit for driving the piezo-electric elements, is provided onthe protective substrate. A driving circuit and the piezo-electricelements are connected to each other by connection lines composed ofconductive wires through lead electrodes, which extend from oneelectrode of the piezo-electric using a wire bonding method.

The protective substrate protects two rows of piezo-electric elementswhich correspond to two rows of pressure generating chambers, with athrough hole formed at the center of the protective substrate throughwhich the connection lines pass. In the ink jet recording head disclosedin Japanese Patent Application No. JP-A-2004-148813, for example, thelead electrodes and the conductive wires are connected to each other inthe through hole.

One problem with such configurations, however, is that the wire bondingmethod used to connect the driving circuit and the piezo-electricelements makes it difficult to reduce the size of the ink jet recordinghead. In addition, since the driving circuit is formed parallel to theprotective substrate, the area of an actuator including thepiezo-electric elements is increased.

In addition, these problems arise in other liquid ejecting heads whicheject liquid materials other than ink.

BRIEF SUMMARY OF THE INVENTION

An advantage of some aspects of the invention is that provides a liquidejecting head and a liquid ejecting apparatus having a compact size.

A first aspect of the invention comprises a liquid ejecting head whichincludes a flow passage forming substrate including pressure generatingchambers which are capable of communicating with nozzles for ejecting aliquid provided therein, pressure generating elements capable ofapplying pressure to eject the liquid in the pressure generatingchambers, lead electrodes capable of supplying electric signals to thepressure generating elements, wiring substrates capable of supplying theelectric signals to the lead electrodes, and a supporting member thatsupports the wiring substrates so as to raise the wiring substrates froma surface of the liquid ejecting head having the lead electrodesprovided thereon.

A second aspect of the invention comprises a liquid ejecting apparatuswhich includes the liquid ejecting head described above.

A third aspect of the invention is a method of manufacturing a liquidejecting head with wiring substrates electrically connected to leadelectrodes in a liquid ejecting head member including a flow passageforming substrate that has includes pressure generating chamberscommunicating with nozzles capable of ejecting a liquid providedtherein, pressure generating elements capable of applying pressure whichcauses the liquid to the pressure generating chambers to be ejected fromthe nozzles, where the lead electrodes supply electric signals to thepressure generating elements. The method comprises fixing the wiringsubstrates to a supporting member to support the wiring substrates,aligning the lead electrodes of the liquid ejecting head member with thewiring substrates, and pressing connecting portions between the alignedlead electrodes and the wiring substrates so as to electrically connectthe lead electrodes and the wiring substrates.

One advantage of the aspects of the invention is that the leadelectrodes of the piezo-electric elements are connected to the wiringsubstrates, making it possible to easily reduce the size of a liquidejecting head as compared to the wire bonding method currently used thatperforms bonding on each wiring line using a bonding tool. In addition,since the wiring substrate is supported by the supporting member,causing it to be raised from the surface of the liquid ejecting headwhere the lead electrodes are provided, it is possible to easily achievea reduction in the size of a liquid ejecting head.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an exploded perspective view illustrating a recording headaccording to a first embodiment of the invention;

FIG. 2A is a plan view illustrating the recording head according to thefirst embodiment of the invention;

FIG. 2B is a cross-sectional view illustrating the recording headaccording to the first embodiment of the invention;

FIG. 3 is an exploded perspective view illustrating a recording headaccording to a second embodiment of the invention;

FIG. 4A is a plan view illustrating the recording head according to thesecond embodiment of the invention;

FIG. 4B is a cross-sectional view illustrating the recording headaccording to the second embodiment of the invention; and

FIG. 5 is a perspective view illustrating a printer which includes arecording head described herein.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view which illustrates the structureof an ink jet recording head, which is an example of a liquid ejectinghead I capable of performing aspects of the invention according to afirst embodiment. FIG. 2A is a plan view of FIG. 1, and FIG. 2B is across-sectional view taken along the line IIB-IIB of FIG. 1.

As shown in FIGS. 1, 2A and 2B, the liquid ejecting head I includes aflow passage forming substrate 10 comprising a (110) silicon singlecrystal substrate, and an elastic film 50 made of a silicon dioxideformed on one surface of the flow passage forming substrate.

Two rows of pressure generating chambers 12 are provided in the widthdirection of the flow passage forming substrate 10. In addition, acommunicating portion 13 is formed in the region outside each row ofpressure generating chambers 12 in the longitudinal direction of theflow passage forming substrate 10. The communicating portion 13 and eachof the pressure generating chambers 12 communicate with each otherthrough an ink supply passage 14 and a communicating passage 15 providedin each of the pressure generating chambers 12. The communicatingportion 13 communicates with a reservoir portion 31 of a protectivesubstrate 30, which is described more fully below, in order to form aportion of a reservoir 100 which serves as an ink chamber that is commonto the two rows of pressure generating chambers 12. The ink supplypassage 14 has a width that is smaller than that of the pressuregenerating chamber 12, which keeps the flow resistance of ink flowingfrom the communicating portion 13 into the pressure generating chamber12 constant. In this embodiment, the ink supply passage 14 is formed byreducing the width of the flow passage by extending one wall of the flowpassage substrate 10 into the ink supply passage 14. However, the inksupply passage may be formed by extending both walls of the flow passagesubstrate 10 into the ink supply passage 14. In addition, the ink supplypassage may be formed by reducing the thickness of the flow passagewithout reducing the width thereof. Each of the communicating passages15 is formed by extending both partition walls 11 of the pressuregenerating chamber 12 to the communicating portion 13 in order topartition a space between the ink supply passage 14 and thecommunicating portion 13. That is, in the flow passage forming substrate10, the ink supply passage 14 has a cross section in the width directionthat is smaller than that of the pressure generating chamber 12 and thecommunicating passage 15 that communicates with the ink supply passage14 has a cross section in the width direction that is larger than thatof the ink supply passage 14. Both the ink supply passage 14 and thecommunicating passage 15 partitioned by a plurality of partition walls11.

A nozzle plate 20 having nozzles 21 formed therein is fixed to an openedsurface of the flow passage forming substrate 10 by, for example, anadhesive or a thermal bonding film. Each nozzle communicates with an endof the corresponding pressure generating chamber 12 opposite to the inksupply passage 14. In this embodiment, since two rows of pressuregenerating chambers 12 are formed in the flow passage forming substrate10, two rows of nozzles 21 are provided in one ink jet recording head I.The nozzle plate 20 is formed of, for example, glass ceramics, siliconsingle crystal, or stainless steel.

As described above, the elastic film 50 is formed on a surface of theflow passage forming substrate 10 opposite to the surface where thenozzles 21 are formed. An insulating film 55 is formed on the elasticfilm 50. In addition, a lower electrode film 60, a piezo-electric layer70, and an upper electrode film 80 are formed on the insulating film 55using a process described more fully below, in order to form apiezo-electric element 300. The piezo-electric element 300 includes thelower electrode film 60, the piezo-electric layer 70, and the upperelectrode film 80. In general, one electrode of the piezo-electricelement 300 serves as a common electrode, and the other electrodethereof and piezo-electric layer 70 are formed in each pressuregenerating chamber 12 by patterning. In this embodiment, apiezo-electric active portion includes the patterned electrode and thepiezo-electric layer 70, such that when a voltage is applied between twoelectrodes, voltage distortion occurs in the piezo-electric activeportion. In this embodiment, the lower electrode film 60 is used as thecommon electrode of the piezo-electric element 300, and the upperelectrode film 80 is used as an individual electrode of thepiezo-electric element 300. However, the electrode structure may bereversed according to a driving circuit and wiring lines. Further, inthis embodiment, the piezo-electric element 300 and a diaphragm that isdeformed by the driving of the piezo-electric element 300 are referredto collectively as an actuator. In this embodiment, the elastic film 50,the insulating film 55, and the lower electrode film 60 serve as thediaphragm, but the invention is not limited thereto. For example, theelastic film 50 and the insulating film 55 may not be provided, and thediaphragm may be comprised of only the lower electrode film 60. Inaddition, the piezo-electric element 300 may also serve as thediaphragm.

The piezo-electric layer 70 is formed on the lower electrode film 60 andis made of a piezo-electric material, which is an electro-mechanicalconversion material. The piezo-electric layer 70 is preferably formed ofa crystal film having a perovskite structure. For example, it ispreferable that the piezo-electric layer 70 be formed of a ferroelectricmaterial, such as lead zirconate titanate (PZT), or a mixture of PZT anda metal oxide, such as a niobium oxide, a nickel oxide, or a magnesiumoxide.

A lead electrode 90 made of, for example, gold (Au), is connected to oneend of each upper electrode film 80, which is an individual electrode ofthe piezo-electric element 300. More specifically, the lead electrode isconnected to the end of each upper electrode film 80 opposite to the inksupply passage 14, and extends onto the insulating film 55. However, theupper electrode film 80 may extend as the lead electrode 90.

A protective substrate 30 having a reservoir portion 31 that forms atleast a portion of the reservoir 100 is bonded to the upper surface ofthe flow passage forming substrate 10 having the piezo-electric elements300 formed therein by an adhesive 35. In this embodiment, the reservoirportion 31 is formed so as to pass through the protective substrate 30in the thickness direction and extend in the width direction of thepressure generating chamber 12. In addition, the reservoir portion 31communicates with the communicating portion 13 of the flow passageforming substrate 10 to form the reservoir 100, which is an ink chambercommon to the pressure generating chambers 12. However, thecommunicating portion 13 of the flow passage forming substrate 10 isdivided into a plurality of portions corresponding to the pressuregenerating chambers 12, and only the reservoir portion 31 serves as thereservoir. In addition, for example, only the pressure generatingchambers 12 are formed in the flow passage forming substrate 10, and theink supply passage 14 that allows the reservoir to communicate with thepressure generating chambers 12 may be formed in a member interposedbetween the flow passage forming substrate 10 and the protectivesubstrate 30, such as, for example, the elastic film 50 or theinsulating film 55.

Piezo-electric element holding portions 32 are provided in a region ofthe protective substrate 30 opposite to the piezo-electric element 300,each having a shape so that the operation of the piezo-electric element300 is not hindered. The piezo-electric element holding portion 32 mayor may not be sealed.

The protective substrate 30 is preferably formed of a material having athermal expansion coefficient that is substantially equal to that of theflow passage forming substrate 10, such as glass or a ceramic material.In this embodiment, a silicon single crystal substrate that is made ofthe same material as that forming the flow passage forming substrate 10is used as the protective substrate 30.

In addition, a through hole 33 passing through the protective substrate30 in the thickness direction is provided in the protective substrate30. Therefore, the ends of the lead electrodes 90 extending from thepiezo-electric elements 300 are exposed through the through hole 33.

Driving circuits 120 that drive the piezo-electric elements 300 aremounted on COF substrates 410, which are wiring substrates. The COFsubstrates 410 are provided substantially in the vertical direction withthe lower ends thereof connected to the lead electrodes 90 and fixed tothe side surfaces of a supporting member 400. In this embodiment, thesupporting member 400 is a rectangular parallelepiped having verticalside surfaces.

Specifically, in the ink jet recording head I according to thisembodiment, two rows of pressure generating chambers 12 are provided inthe flow passage forming substrate 10, and two rows of piezo-electricelements 300 are provided in the width direction of the pressuregenerating chamber 12. That is, two rows of the pressure generatingchambers 12, piezo-electric elements 300, and the lead electrodes 90 arearranged opposite to each other in a symmetrical configuration. Inaddition, two COF substrates 410 are fixed to both side surfaces of thesupporting member 400 having a lower part inserted into the through hole33, and each of the COF substrates 410 is provided substantially in thevertical direction with the lower end thereof connected to the leadelectrodes 90. A buffer member 420 that is preferably made of Teflon® isprovided on a lower surface of a SUS member of the supporting member400. The lower ends of the COF substrates 410 and the lead electrodes 90are electrically connected to each other by conductive particlesincluded in an anisotropic conductive layer, such as an anisotropicconductive film or an anisotropic conductive paste.

More specifically, after the anisotropic conductive layer is formed onthe lead electrodes 90, the positions of the lead electrodes 90 and theCOF substrates 410 fixed to the supporting member 400 are adjusted sothat the corresponding wiring lines are opposite to each other, and thesupporting member 400 is pressed such that the lower surface of thesupporting member presses the COF substrates 410 against the leadelectrodes 90. In this way, predetermined electrical connection is madebetween the COF substrates 410 and the lead electrodes 90 by conductiveparticles. In this case, the buffer member 420 functions to apply auniform pressing force to the COF substrates 410. It is preferable thatthe lower surface of the supporting member 400 and the lower ends of theCOF substrates 410 have a profile irregularity that is less than fivetimes the diameter of the conductive particle. In this case, it ispossible to apply a uniform pressing force to the conductive particlesusing the buffer member 420 and the lower ends of the COF substrates410. As a result, it is possible to reliably press the conductiveparticles to ensure good electrical connection.

It is preferable that the supporting member 400 be formed of a materialhaving a thermal conductivity capable of reducing the temperature of thedriving circuit to be lower than a junction temperature even when theink jet recording head I is operating at a maximum operation temperatureat which the ink jet recording head I is guaranteed to operate. In thiscase, a sufficient dissipation effect is obtained even when the drivingcircuit is operated under the most severe load conditions. As a result,it is possible to stably operate the driving circuit for a long time.For this reason, in this embodiment, the supporting member 400 is formedof a SUS material. In this case, ink flowing through the flow passageforming substrate 10 can absorb heat generated from the driving circuits120 through the supporting member 400. As a result, it is possible toeffectively dissipate heat generated from the driving circuits 120. Theabove-mentioned effect and operation can be obtained by sufficientlyreducing the distance between the surface of the flow passage formingsubstrate 10 and the driving circuit 120 or mounting the drivingcircuits 120 to the COF supporting member 400, even when a metalmaterial, such as SUS, is not used. That is, it is preferable that thedistance between the driving circuit 120 and the surface of the flowpassage forming substrate 10 be set to a value so that the ink iscapable of dissipating heat from the driving circuit 120 so that thetemperature of the driving circuit 120 is lower than its junctiontemperature even when the liquid ejecting head I is used at the maximumoperation temperature, or the driving circuit be directly connected tothe supporting member 400.

A compliance substrate 40 including a sealing film 41 and a fixing plate42 is bonded to the protective substrate 30. The sealing film 41 isformed of a material having low rigidity and flexibility, such as, forexample, polyphenylene sulfide (PPS), and the sealing film 41 seals onesurface of the reservoir portion 31. The fixing plate 42 is formed of ahard material, such as metal, for example, stainless steel (SUS). Aregion of the fixing plate 42 opposite to the reservoir 100 forms anopening portion 43 that is formed in the thickness direction. Therefore,one surface of the reservoir 100 is sealed by only the flexible sealingfilm 41.

In the ink jet recording head according to this embodiment, ink is drawnfrom an ink inlet connected to an external ink supply unit (not shown),causing a space from the reservoir 100 to the nozzles 21 to fill withink. Then, a voltage is applied between the lower electrode film 60 andthe upper electrode film 80 corresponding to each pressure generatingchamber 12 according to recording signals transmitted from the drivingcircuit 120. This causes the elastic film 50, the insulating film 55,the lower electrode film 60, and the piezo-electric layer 70 to deform.Then, the internal pressure of each pressure generating chamber 12 isincreased, and ink droplets are discharged from the nozzles 21.

Further, according to this embodiment, the driving circuits 120 and thelead electrodes 90 of the piezo-electric elements 300 are connected toeach other by the COF substrates 410 having the driving circuits 120mounted thereon. Therefore, it is possible to more easily manufacture anink jet recording head, as compared to the wire bonding method currentlyused in the art. In addition, since the COF substrate 410 is providedsubstantially in the vertical direction with its lower end connected tothe lead electrodes 90, it is possible to easily achieve a reduction inthe size of an ink jet recording head. Further, since the drivingcircuits 120 are fixed to the side surfaces of the supporting member 400with the COF substrates 410 interposed therebetween, it is possible toeffectively dissipate heat generated from the driving circuits 120.

FIG. 3 is an exploded perspective view schematically illustrating thestructure of an ink jet recording head II, which is an example of aliquid ejecting head according to a second embodiment of the invention.FIG. 4A is a plan view of FIG. 3, and FIG. 4B is a cross-sectional viewtaken along the line IVB-IVB of FIG. 3.

As shown in FIGS. 3, 4A, and 4B, an ink jet recording head II accordingto this embodiment is similar to the ink jet recording head I of thefirst embodiment shown in FIGS. 1, 2A, and 2B except that the supportingmember 401 is modified. In this embodiment, the same components as thoseshown in FIGS. 1, 2A, and 2B are denoted by the same reference numerals,and a description thereof will be omitted.

As shown in FIGS. 3, 4A, and 4B, the supporting member 401 according tothis embodiment is formed by bonding the rear surfaces of two supportingmembers 401 a and 401 b. When the two supporting members 401 a and 401 bare used, for example, the COF substrates 410 having the drivingcircuits 120 mounted thereon are bonded to the side surfaces of thesupporting members 401 a and 401 b, and the lower ends of the substratesare bent so as to come into contact with the lower surfaces of thesupporting members 401 a and 401 b. In this state, the COF substrates410 bonded to the supporting members 401 a and 401 b are individuallyaligned with the lead electrodes 90. Then, the supporting members 401 aand 401 b are pushed against the conductive particles, thereby ensuringelectrical connection between the lead electrodes 90 and the supportingmembers. Thereafter, the rear surfaces of the two supporting members 401a and 401 b are bonded together to form one supporting member.

According to this embodiment, it is possible to individually adjust thealignment between the COF substrates 410 and the lead electrodes 90 atboth sides of the supporting member 401. Therefore, it is possible toeasily perform a predetermined alignment operation.

Other Embodiments

In the above-described embodiments, two rows of pressure generatingchambers 12 are provided in the flow passage forming substrate 10, butthe number of rows of pressure generating chambers is not limited tothis configuration and any number of rows may be formed. For example,one or three or more rows of pressure generating chambers may beprovided. When a plurality of rows of pressure generating chambers areprovided, at least a set of two rows of pressure generating chambers maybe provided opposite to each other.

Further, in the above-described embodiments, the supporting members 400and 401 are pressed against the conductive particles. However, a memberother than the supporting member may be used to press the conductiveparticles, and the wiring substrates may be fixed to supporting memberafter the pressing process.

Furthermore, in the above-described embodiments, the driving circuits120 are mounted to the supporting members 400 and 401. However, in orderto achieve high-density mounting without performing connection using awire bonding method, the wiring substrates connected to the leadelectrodes 90 may be supported by the supporting member 400 and 401 soas to be raised from the surface having the lead electrodes 90 providedthereon. In this case, the supporting members 400 and 401 may be formedin any shape, so long as they serve a supporting function. For example,the supporting member may have a lattice shape or a raft shape. However,when the supporting member is pushed to press the conductive particles,it is preferable that the lower surface of the supporting member be flatin order to apply a uniform pressing force. Alternatively, the drivingcircuits 120 may be directly mounted to the supporting members 400 and401, and the wiring substrates may be connected to the surfaces of thedriving circuits 120. In this case, the lower parts of the wiringsubstrates are bent to the sides opposite to the supporting members 400and 401 and then connected to the lead electrodes 90.

The material forming the flow passage forming substrate 10 is notlimited to that according to the above-described embodiments.

In the above-described embodiments, the ink jet recording head is givenas an example of the liquid ejecting head. However, the invention can beapplied to all kinds of liquid ejecting heads. For example, theinvention may be applied to a liquid ejecting head that ejects liquidother than ink. Other examples of the liquid ejecting head include, forexample, various kinds of recording heads used for image recordingapparatuses, such as printers, a color material ejecting head used tomanufacture, for example, a color filter of a liquid crystal display, anelectrode material ejecting head used to form, for example, electrodesof an organic EL display or a field emission display (FED), and abioorganic material ejecting head used to manufacture a biochip.

The ink jet recording head according to the above-described embodimentsforms a portion of a recording head unit that has an ink flow passagecommunicating with, for example, an ink cartridge, and is provided in anink jet recording apparatus. FIG. 5 is a diagram schematicallyillustrating an example of the ink jet recording apparatus. As shown inFIG. 5, recording head units 1A and 1B, each comprising a ink jetrecording head I according to the above-described embodiment, areprovided such that cartridges 2A and 2B forming an ink supply unit canbe inserted into or removed from the recording head units. Additionally,a carriage 3 having the recording head units 1A and 1B mounted thereonis provided so as to be movable in the axial direction of a carriageshaft 5 attached to a main body 4. The recording head units 1A and 1Beject, for example, a black ink composition and a color ink composition,respectively.

The driving force of a driving motor 6 is transmitted to the carriage 3through a plurality of gears (not shown) and a timing belt 7 to move thecarriage 3 having the recording head units 1A and 1B mounted thereonalong the carriage shaft 5. A platen 8 is provided along the carriageshaft 5 in the main body 4, and a recording sheet S, such as paper,which comprises a recording medium, is fed by, for example, a sheet feedroller (not shown). The sheet S is transported by the platen 8. Thedriving motor 6 or the pressure generating units of the recording headunits 1A and 1B are controlled by a control unit (not shown) including,for example, a CPU and a memory.

1. A liquid ejecting head comprising: a flow passage forming substrateincluding pressure generating chambers which are capable ofcommunicating with nozzles for ejecting a liquid provided therein;pressure generating elements capable of applying pressure to eject theliquid in the pressure generating chambers; lead electrodes capable ofsupplying electric signal to the pressure generating element; wiringsubstrate capable of supplying the electric signal to the leadelectrode; and a supporting member that supports the wiring substrate soas to raise the wiring substrate from a surface of the liquid ejectinghead having the lead electrodes provided thereon, wherein a surface ofthe wiring substrate and the surface of the liquid ejecting head meet atan angle.
 2. The liquid ejecting head according to claim 1, wherein thewiring substrate is formed perpendicular to the surface of the liquidejecting head.
 3. A liquid ejecting apparatus comprising the liquidejecting head according to claim 1.